In a color video display system such as a video tape recorder in which low-frequency converted color signals are recorded, a composite color video signal is separated into luminance and chrominance components before the signal is to be processed. In a noise reduction circuit used in such a system, a luminance signal containing noises is fed to a high-pass filter to extract therefrom high-frequency components containing the noises. Noise components of limited amplitudes are derived from the the resultant output signal from the high-pass filter. The noise components are, upon phase inversion, added to the original luminance signal. The noises in the two signals are thus cancelled by each other so that a noise-free luminance signal is obtained.
When a composite color video signal is used as an input signal for such a noise reduction circuit, the high frequency components extracted from the signal supplied to the high-pass filter contain not only the noise components but the chrominance signals of the frequency which falls within the frequency band of the noise components. If the chrominance signal has an amplitude larger than the threshold value of the amplitude limiter used, then the amplitude limiter would be saturated with such chrominance signals and would be disabled from passing the noise components therethrough.
A video disc player (VDP) uses composite color video signals which are recorded on a record medium not in forms separated into luminance and chrominance components. If a noise reduction circuit of the described nature is to be used in such a system, it is thus necessary to add to the noise reduction circuit a network to separate the information read from the record medium into luminance and chrominance signal components. A known form of luminance-chrominance separation network used for this purpose is a comb filter which uses a charge-coupled device providing a time delay lasting for one scanning period. The provision of such a network however causes deterioration of the signals used and results in, for example, deformation of the signal waveforms, degradation of the signal-to-noise ratio as invited by the CCD device per se or by the leaks of clock pulses applied to the CCD device, an increase in the production cost, and so on. A goal of the present invention is to make it possible to remove noises directly from raw composite color video signals without separating the composite video signals into luminance and chrominance components.